This invention concerns arrays of magnetic recording heads for use in magnetic printing applications. More specifically, this invention concerns arrays of recordings heads comprising a plurality of active pin poles and a passive sheet pole.
Machines for producing printed copy from a latent image which is recorded on a magnetic medium are well known to the reproduction arts. Typically, an original image is optically scanned to produce an electrical signal which varies in intensity with the brightness of the original image. The electrical signal, which may for example be stored and regenerated in a computer memory, is applied to magnetic recording heads which produce a sequentially varying magnetic field. The surface of a magnetic recording medium, for example, a drum or an oxide coated tape, moves past the recording heads through the varying magnetic field. A latent magnetic image corresponding to the brightness of an original image is thus recorded in the surface of the magnetic medium. A magnetic ink which may be in the form of dry particles comprising finely divided ferromagnetic powder and a thermoplastic resin, is applied to the surface of the recording medium where it is attracted by the magnetic field variations of the latent image. The ink image is then transferred from the magnetic medium to a final copy material, typically paper, by any of a variety of well known processes which include electrostatic transfer and pressure transfer. The latent magnetic image may then be re-inked for printing additional copies or erased to permit the recording medium to be used for printing a new image.
The resolution of a magnetic printing system increases with the number of separate picture elements recorded in a given area, and therefore, decreases with the size of the picture elements. In one embodiment of a magnetic printing system, a linear array of recording heads is used to record a line of picture elements on the recording medium. The recording medium moves past the recording heads and a series of such lines generate a two-dimensional image. The resolution along such a line is inversely proportional to the spacing between recording heads in the array. High resolution printing, therefore, requires a recording head array with small center-to-center spacing between heads.
Typical magnetic printing systems of the present art require linear arrays including hundred or thousands of recording heads. Such arrays can be most economically produced as integrated assemblies.
One conventional embodiment of a recording head array for use in magnetic printing systems comprises pairs of permeable pin cores which are wrapped with field coils to form recording head poles. Magnetic fields for recording are induced between the poles of each pin pair.